Add documentation for Tab plugin's `show` method

v4: Drop pager component

Erratum from #18778
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Erratum from #18658
[ci skip]

fixes #18658: no more min-width action on progress bars. we had them in v3 and ended up removing them for additional problems it caused folks.

Set -ms-overflow-style:scrollbar to workaround apparent IE11+Edge @viewport bug

Remove usages of and references to <input type="datetime">

It has been removed from the HTML specification: https://github.com/whatwg/html/issues/336
Only Presto Opera ever implemented a special UI for it.

[skip sauce]

/fyi @mdo

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Closes #18543

v4: Rename .card-*-outline to .card-outline-*

Document .card-*-outline variants

Added !important to hover

.container, .container-fluid should be conditional upon $enable-grid-…

README: Add badges for Packagist and Atmosphere

v4: Rename .btn-*-outline to .btn-outline-*

fix justified navbar

v4: Custom forms (disabled state, revamp, etc)

- add more details on custom checkboxes and radios for how we handle the states and how the css works
- create a disabled custom checkboxes and radios example